A standard filament-working machine such as a spinning apparatus takes a filament, roving or the like, out of a container, hereinafter referred to as a can, acts on it, and returns the treated filament to another can. Thus the machine typically has an input location that must be supplied with a succession of full cans of filament as cans are emptied and moved out of the way and an output location from which the full cans must be taken away and replaced with empty ones. For maximum efficiency it is imperative that the machine run continuously, to which end it is therefore necessary to make the changeover from one can to the next at both the input and output stations as quickly as possible.
In German patent document 3,634,683 filed Oct. 11, 1986 and assigned to Lippert GmbH a system is shown which has a transporter that extends between a drawing frame and a plurality of rotor-type spinning machines. The cans filled with filament at the drawing frame are conveyed by means of a transport device to one of the spinners and set down there. Subsequently empty cans are transported back from the spinners and refilled with filament. The transport device stays in position on the drawing frame with filled cans until a sensor determines that there is an empty can at a spinner whereupon the transporter moves to the empty-can location and switches the empty can for a full one.
To reduce switchover time it is standard to provide at each station one or more extra waiting positions where full cans may sit before they are needed or empty cans can sit before they are taken away. These waiting positions are tended automatically by a combination conveyor/transfer device. Swiss patent 389,461 filed Nov. 1, 1961 by I. Kaino et al describes such a system wherein once all the filament is removed from a row of cans, they are automatically transported away and replaced with a new row of filled cans.
German patent document 3,618,857 filed June 4, 1986 by F. Molders described a pivotal grab system that moves empty cans into the loading position of a spinning machine and full cans away from this machine. This arrangement facilitates automatic handling of such cans. Such a system, like the others above, relies on the conveyor being able to work so fast that it can keep ahead of the needs of the machines it is servicing no matter how quickly these machines operate.